Examination of new fossils (humerus and sacrum) from The Netherlands reveals morphologically-distinctive characters, allowing the description of a new Late Miocene — Early Pliocene representative (Praepusa boeska sp.n.) of the subfamily Phocinae. Diagnostic humeral diff erences in shape of the coronoid (oval in males vs triangular in females) and depth of the olecranon fossae (shallow in males vs deep in females), as well as the presence of a rounded fi rst ventral foramen and thick lateral wall in the male sacrum, reveal the fi rst evidence of sexual dimorphism in the genus Praepusa. The newly described species adds information on the distribution of true seals, supporting the westward dispersal of this genus across the Paratethys. Strong endemism from closure of the Paratethys, and climatic, geological and stratigraphic diff erences indicate that Praepusa first inhabited the Eastern Paratethys (Early — Middle Miocene, 16.5–13.6 Ma) before dispersing to the Central (Middle Miocene, 13.6–11.2 Ma) and, later, Western (Late Miocene — Early Pliocene, 11.6–3.6 Ma) Paratethys. The Pr. boeska fossils are the youngest to date and have been found the furthest west of any previously described material of this genus. Th ese fi ndings help explain the origin and dispersal among described species of the genus Praepusa in comparison with other genera of the subfamily Phocinae.